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The Asteroid Threat: Understanding the Stakes

Part 2 of a series

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Former astronaut Ed Lu, the chief executive of the B612 Foundation, a northern California group attempting to build the privately financed “Sentinel” asteroid-detecting space telescope, addressed the implications of large asteroid hits in April testimony before the House Science, Space and Technology Committee.

“If you wanted a really serious effort, you would give NASA a relatively modest increase in budget,” says Dr. Scott Pace, Director of George Washington University’s Space Policy Institute. “The additional funds could accelerate the time for finding potential hazards and understanding of the risks actually facing the Earth.  Is there really something out there that we have to worry about in the next decade? If there is, we need to know now. If not, we can focus on doing science while monitoring for future risks.”

“The impact of a one kilometer or larger asteroid would have energy of forty thousand megatons, and would likely end human civilization regardless of where on the Earth it occurs,” said Lu, whose foundation is named for the home asteroid of the hero in Antoine de Saint-Exupery’s book The Little Prince. “However, smaller yet still potentially catastrophic asteroids are still largely not tracked. For example, the impact of a 140-meter asteroid would release several times more energy than all the munitions used in World War II.  Yet we have only observed and tracked less than 10 percent of asteroids in this size range… We have only observed and tracked less than one percent of asteroids in the 40-meter 1908 Siberian asteroid size range.  We have the technology to deflect asteroids to prevent an impact on Earth, but this technology is useless until we find asteroids first. We cannot deflect (or for that matter capture, visit, or explore) an asteroid that we haven’t yet found.  We simply do not know when the next catastrophic asteroid impact will be, because we have not yet tracked the great majority of asteroids.”

Back in 2010, the NASA Advisory Council Ad Hoc Task Force on Planetary Defense summarized the list of asteroid known-knowns, known-unknowns and unknown-unknowns – as Donald Rumsfeld might put it – thusly:  “NASA’s search for near-Earth objects has discovered at least 87 percent of the large asteroids whose impacts could pose a global threat to our civilization. None pose a credible threat of a collision with the Earth for the foreseeable future. But the discovery rate of the much more numerous smaller NEOs, representing a regional or local impact hazard, will soon confront us with objects presenting worrisome but uncertain probabilities for a future collision with Earth. Such situations will appear more frequently as the discovery rate increases, and the nation presently has no clear policy on how to address such a situation.”

 

Where Does Asteroid Detection Fit in NASA’s Priorities?

Clearwater Lakes craters

These twin circular lakes (large dark features) were formed simultaneously by the impact of an asteroidal pair which slammed into the planet approximately 290 million years ago. The lakes (or lake, since it is a single body of water) are located near the eastern shore of Hudson Bay within the Canadian Shield in a region of generally low relief in northern Québec province. Their proper French name is Lac à l’Eau Claire. Notice that the larger western structure contains a ring of islands that surrounds the center of the impact zone. The lakes are named after their exceedingly clear water. Science and Analysis Laboratory, NASA-Johnson Space Center image

When I worked at NASA in the last decade, we often used the tagline, “as only NASA can,” to describe the variety of tasks that the world’s premier space agency conducts. To be certain, some of NASA’s missions, such as human space exploration, are not designed nor expected to result in immediate tangible benefits for the public, except through the serendipity of technological spinoffs. But NASA historically had mission goals that directly serve the public interest, such as aeronautics research, Earth science observations, and asteroid detection. Should the space agency be doing more in this regard, even if, from a purely self-interested standpoint, since our nation’s surface area only covers two percent of the Earth’s surface we stand less to risk from the occasional small asteroid intruder?

“If you wanted a really serious effort, you would give NASA a relatively modest increase in budget,” says Dr. Scott Pace, Director of George Washington University’s Space Policy Institute. “The additional funds could accelerate the time for finding potential hazards and understanding of the risks actually facing the Earth. Is there really something out there that we have to worry about in the next decade? If there is, we need to know now. If not, we can focus on doing science while monitoring for future risks.”

“Maybe when they [Congress] hear that it’s a very modest amount of money required to do the comprehensive space search, they will find the resources to fund it. We estimated in our task force that for one-sixtieth of the NASA budget over 10 years, we could do the space search and a demonstration required to give you confidence that you could deflect a future asteroid impactor. Then the budget would drop to a low level, because you’ve already done the demo and the technology development is on the shelf.  I think that was a very reasonable proposal – something on the order of $200 million a year for ten years.”

Former astronaut Thomas Jones, who chairs the Committee on Near Earth Objects for the Association of Space Explorers, a global organization of astronauts and cosmonauts, and who co-chaired the 2010 NASA Advisory Council Task Force on Planetary Defense, puts the funding issue in perspective: “Maybe when they [Congress] hear that it’s a very modest amount of money required to do the comprehensive space search, they will find the resources to fund it. We estimated in our task force that for one-sixtieth of the NASA budget over 10 years, we could do the space search and a demonstration required to give you confidence that you could deflect a future asteroid impactor. Then the budget would drop to a low level, because you’ve already done the demo and the technology development is on the shelf. I think that was a very reasonable proposal – something on the order of $200 million a year for ten years.”

Technically, says Jones, the problem with finding potentially hazardous asteroids from the ground is “they are either small and thus dim, or they are far away from us, or they come from the daylight side of the Earth where our night-operating telescopes don’t work. And that’s a real constraint. You’ve got weather to deal with for ground-based telescopes, and you’ve got this daytime sky problem where you can’t detect asteroids at all. They are just too dim. That’s a real roadblock. Unless NASA goes to some really premier ground-based facilities, even the ones on the drawing boards now won’t do that 140-meter job until 2030 at the earliest.

The alternative is a space-based telescope which has much more efficiency,” Jones says, adding, however, that where you put a space-based telescope is critical. “Ideally you want that space-based telescope to not be in Earth orbit, because it’s only able there to look at objects that are really farther from the sun than the Earth is.  It really can’t stare too close to the sun because of the sun’s brilliance. The goal is a Venus-like parking orbit about 70 million miles from the Sun. That’s a nice characteristic, because then you can stare out past the Earth and you can see the clouds of asteroids that are between Venus and the Earth which could be coming and smacking the Earth from the day side, like the Chelyabinsk object. If you park the spacecraft there and search for a number of years you would get a lot of the smaller asteroids. You could look at 90 percent of those 140-meter objects within five years after starting the mission. It could have that catalog filled out soon after 2020.  And the nice thing is you could find a lot of other small ones. There are about a million of those city killers; you’d make a good dent in that population as well. And the longer you operate that telescope the more of those you will get.”

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Edward Goldstein has more than 20 years' experience in the U.S. space community. From...